Vehicles of different types mostly comprise two different braking systems. One of said braking system serves for reducing the velocity of the vehicle during driving and it is hydraulically or pneumatically operated, for example, via a pedal. The other braking system is used for securing the vehicle during parking. In this brake system, the brakes are mainly operated via brake cables which are set under tensile loads by means of different lever mechanisms in the vehicle compartment. These brakes are also designated as handbrakes or lever brakes.
The prior art provides different solutions of mechanisms for operating parking brakes which are driven either by hand or by foot. Since sometimes substantial forces are needed to operate the parking brake, it is often not applied in the needed extent so that the vehicle can roll away in the parked state. Thereby, a high security risk is generated in traffic. On the other hand, it is also inconvenient for the driver to apply the parking brake with a high effort. For this reason, mechanisms for operating a parking brake were developed which are driven by an electric motor.
Although, it is convenient for the driver to use a parking brake with an electric operating mechanism, the construction of the parking brake and of the operating mechanism has to be protected against potential mechanical overload conditions so that for instance a defect of the motor does not lead to a damage or a destruction of the system. In this context, the WO 98/56633 discloses an electric operating mechanism with load sensor for a parking brake. This arrangement consists of an electric motor for the operation of a setting unit which is used for tightening or releasing a brake cable of a brake. The brake cable is connected with a setting unit via a load sensor so that the force exerted by the setting unit is directly transmitted and determined by the load sensor. It is a substantial disadvantage in this arrangement that the force transmission from the setting unit to the brake cable is disconnected in case of a failure of said load sensor. Therefore, an operation of the brakes is no longer possible which leads to a high risk in traffic. Additionally, the production of said operating mechanism of the present parking brake is expensive due to its complex construction.
It is, therefore, the problem of the present invention to provide an operating mechanism for a brake the construction of which meets higher security requirements and which, even though, comprises a simple construction. It is a further problem of the operating mechanism of the brake to reduce the expenditure of maintenance due to a more compact arrangement of the single components.